It is common in communications engineering to transmit information through conventional electrical cables. Such a cable may contain a large number of conductors with numerous information channels. However, such communication cables are very limited in their transmission capacity since the transmission band width of each conductor, as well as the possible number of conductors which can be combined in a cable, is limited.
Optical wave guides have substantially wider transmission bands. In addition they are very thin, and it would appear possible to combine a considerable number of such wave guides within one cable and thus to obtain a far greater transmission capacity than with conventional communication cables.
However, it is not possible to simply combine these optical wave guides in the same manner as a prior-art electric communication cable, and it is thus important to design communication cables which are to be used in connection with optical fibers.